Composite structures constructed of wound tubular braiding

ABSTRACT

A system for constructing a composite structure includes a braiding machine, a winding tool and a forming machine. The composite structure is constructed of a wound tubular braiding. The wound tubular braiding is constructed of a biaxial or triaxial tubular braid of unidirectional tape.

INTRODUCTION

The present disclosure relates to composites structures. Morespecifically, the present disclosure relates to a composite structureconstructed of wound tubular braiding.

BACKGROUND

An increasing number of composite materials are being used on aircraft.Composite materials typically include reinforcing fibers bound to apolymer resin matrix. The fibers may be unidirectional. Alternatively,the fibers may take the form of a woven cloth or fabric. The fibers andpolymer resin are arranged and cured to form a composite structure. Someexamples of composite materials that may be used in an aircraft includeaircraft windows and door frames.

There are various challenges that exist when fabricating compositestructures using conventional processes. For example, circular orelliptical composite components may require specific lay-up schemes tocreate lay-ups. The lay-up schemes are often controlled by thelimitation of existing processes. Examples of these existing processesinclude fiber placement or fabric making machines. However, fiberplacement or fabric making machines are typically tailored specificallyfor a particular configuration or final structure of the finishedproduct. Current processes based on automated fiber placement or wovenfabric are costly, time consuming, and may not be advantageous forcomponents having tight radii.

Some composite components require a hole or aperture defined within thestructure. For example, aircraft window frames define an aperture. Itmay be especially difficult and laborious to orient the reinforcingfibers for a composite component having an aperture. Additionally, whenconventional manufacturing processes are used to fabricate a compositecomponent having an aperture, relatively large amounts of material wastemay be produced.

Thus, while current methods and systems for fabricating compositestructures achieve their intended purpose, there is a need for anew andimproved system and method of fabricating composite structures.

SUMMARY

According to several aspects, a composite structure is disclosed. Thecomposite structure includes a formed winding of tubular braiding.

In another aspect of the present disclosure, a composite structureincluding a biaxial braiding that is formed into a winding is disclosed.

According to several aspects, a composite structure including a tubularbraiding that is biaxially braided is disclosed.

In another aspect of the present disclosure, a composite laminatestructure including a plurality of plies is disclosed. The compositestructure includes biaxially braided fibers oriented in the samedirection for each of the plurality of plies.

In yet another aspect of the present disclosure, a braiding machine isdisclosed and includes a mandrel, a braiding mechanism having spoolseach moveable relative to the mandrel, a unidirectional tape woundaround each of the spools, a guide ring, and a control module. The guidering directs the unidirectional tape wound around a corresponding spoolonto the mandrel. The control module is in electronic communication withthe braiding mechanism. The control module executes instructions toguide movement of the plurality of spools to place the unidirectionaltape onto the mandrel to create a tubular braiding.

In still another aspect of the present disclosure, an apparatus forfabricating a composite structure of wound tubular braiding isdisclosed. The apparatus includes a tool defining an outer surface, adevice to wind the tubular braiding around the outer surface of the toolto create a composite preform, a forming device to consolidate thecomposite preform, and a control module. The control module is inelectronic communication with the device and the forming device. Thecontrol module executes instructions to guide the device to wind thetubular braiding around the outer surface of the tool and operate theforming device to consolidate the composite preform.

According to several aspects, a method of forming a composite structureis disclosed. The method includes forming a wound tubular braiding intothe composite structure.

In still another aspect of the disclosure, a method of fabricating acomposite preform is disclosed. The method includes winding a tubularbraiding of unidirectional fibers while allowing the unidirectionalfibers shift to relative to one another without bending.

In another aspect of the disclosure, a method of forming a tubularbraiding is disclosed. The method includes braiding unidirectional tapeinto the tubular braiding.

In another aspect of the disclosure, a wound tubular braiding for acomposite structure is disclosed. The wound tubular braiding includes atubular braiding wound into a helical shape.

The features, functions, and advantages that have been discussed may beachieved independently in various embodiments or may be combined inother embodiments further details of which can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic diagram of a system for constructing compositestructures, according to an exemplary embodiment;

FIG. 2 is a schematic diagram of a braiding machine for fabricating atubular braiding according to an exemplary embodiment;

FIG. 3 is the braiding machine shown in FIG. 2 viewed in the directionof section line 3-3, according to an exemplary embodiment;

FIG. 4 is an enlarged view of a unidirectional tape, indicated bysection line 4-4 in FIG. 3, according to an exemplary embodiment;

FIG. 5 is a perspective view of a portion of a tubular braiding having abiaxial braid fabricated by the braiding machine shown in FIGS. 2 and 3according to an exemplary embodiment;

FIG. 6 is a perspective view of a portion of a tubular braiding having atriaxial braid fabricated by the braiding machine shown in FIGS. 2 and 3according to an exemplary embodiment;

FIG. 7 is an exemplary process flow diagram illustrating a method offorming the tubular braiding using an inflatable mandrel, according toan exemplary embodiment;

FIG. 8 is an exemplary process flow diagram illustrating a method offorming the tubular braiding using a non-inflatable mandrel, accordingto an exemplary embodiment;

FIG. 9 is front perspective view of a winding tool, according to anexemplary embodiment;

FIG. 9A is an alternate embodiment of a cross section of the windingtool viewed in the direction of section line 9A-9A in FIG. 9, accordingto an exemplary embodiment;

FIG. 9B is another alternate embodiment of a cross section of thewinding tool viewed in the direction of section line 9B-9B in FIG. 9,according to an exemplary embodiment;

FIG. 10 is front perspective view of the winding tool with a woundtubular braiding disposed thereon, according to an exemplary embodiment;

FIG. 11 is front perspective view of the wound tubular braiding,according to an exemplary embodiment;

FIG. 12 is a front perspective view of a forming machine in an openposition, according to an exemplary embodiment;

FIG. 13 is a cross-section view of the forming machine in a closedposition viewed in the direction of section line 13-13 in FIG. 12,according to an exemplary embodiment;

FIG. 14 is a front perspective view of the forming machine in the openposition with the wound tubular braiding loaded therein, according to anexemplary embodiment;

FIG. 15 is a cross-section view of the forming machine in the openposition with the wound tubular braiding loaded therein viewed in thedirection of section line 15-15 in FIG. 14, according to an exemplaryembodiment;

FIG. 16 is a cross-section view of the forming machine in the closedposition with the wound tubular braiding loaded therein viewed in thedirection of section line 16-16 in FIG. 14, according to an exemplaryembodiment;

FIG. 17 is a top view of the composite structure, according to anexemplary embodiment;

FIG. 18 is a cross-section view of the composite structure viewed in thedirection of section line 18-18 in FIG. 17;

FIG. 19 is an exemplary process flow diagram illustrating a method offorming the composite structure, according to an exemplary embodiment;

FIG. 20 is an exemplary process flow diagram illustrating a method ofwinding the tubular braiding, according to an exemplary embodiment;

FIG. 21 is a flow diagram of aircraft production and servicemethodology; and

FIG. 22 is a block diagram of an aircraft.

DETAILED DESCRIPTION

A composite structure constructed of a formed winding of tubularbraiding is disclosed. The tubular braiding is constructed of aunidirectional tape or a unidirectional tow of unidirectional fibers. Abraiding machine for fabricating the tubular braid is also disclosed.The braiding machine includes a braiding mechanism and a mandrel. Aplurality of spools having unidirectional tape or unidirectional towwound around each spool are mounted to the braiding mechanism. Thebraiding mechanism controls placement of the unidirectional tape orunidirectional tow from the spools and onto the mandrel to create thetubular braiding. The tubular braiding may have a biaxial braid or atriaxial braid.

An apparatus for fabricating the composite structure by winding thetubular braiding around a tool is also disclosed. In one embodiment, thebraiding is first removed from the mandrel and wound around an outersurface of the tool to create a wound tubular braiding. In anotherembodiment, the mandrel remains with, and forms part of, the woundtubular braiding. In yet another embodiment, the tubular braiding isslit to remove the mandrel. The unidirectional tape or unidirectionaltow are not constricted as the tubular braiding is wound around thetool. In other words, the unidirectional tape or unidirectional towslips or shears relative to one another as the tubular braiding is woundaround the tool. This relative slippage or shearing of theunidirectional tape or unidirectional tow permits the construction ofstructures without wrinkling yet having fiber direction orientatedadvantageously relative to the final structure. The wound tubularbraiding is then removed from the tool and is heated and compacted flatby a forming machine to create the composite structure. Once again, theunidirectional tape or unidirectional tow are not constricted and slipor shear relative to one another as the tubular braiding is compactedflat.

Allowing the unidirectional fibers to slip or shear relative to oneanother during winding and consolidating the composite preform resultsin a composite structure having more fibers orientated advantageouslyrelative to the structure per ply of laminate being created. Moreover,the resulting composite structure also requires fewer plies of laminateto achieve strength goals since more fibers are orientatedadvantageously relative to structure per ply of laminate makes thestructure more efficient This in turn results in weight reduction of thecomponent. The disclosed process of creating the composite structure israpid when compared to conventional lay-up processes, which in turnenables higher production rates. Furthermore, the disclosed process forcreating the composite also results in reduced waste and labor intensivepost-processing machining when compared to conventional processes.

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring to FIG. 1, a schematic diagram of a system 10 for constructingcomposite structures is shown. The system 10 generally includes tooling12 and work product 14 upon which the tooling 12 interacts. The tooling12 includes a braiding machine 16, a winding tool 18, and a formingmachine 20. The work product 14 includes a tubular braiding 22, a woundtubular braiding 24, and a composite structure 26. The wound tubularbraiding 24 may also be referred to as a winding of tubular braiding.The tubular braiding 22 is formed by the braiding machine 16. The woundtubular braiding 24 is formed by the winding tool 18 from the tubularbraiding 22. The composite structure 26 is formed by the forming machine20 from the wound tubular braiding 24. The composite structure 26 is anyframe that surrounds and provides support to an aperture that requires aspecific fiber orientation and lay up to meet design requirements. Forexample, the composite structure 26 may be a window frame for anaircraft, a door frame for an aircraft, etc. The tooling 12 may includeother machines, such as molding or post-processing machines, cuttingdevices, etc., without departing from the scope of the presentdisclosure. Likewise, the work product 14 may include additionalvariations of the tubular braiding 22, wound tubular braiding 24, andcomposite structure 26. The system 10 may be employed in the context ofaircraft manufacturing and service, as will be described below. Forexample, the system 10 may be used in component and subassemblymanufacturing of an aircraft including an airframe and interior, systemintegration of the aircraft, and routine maintenance and service of theaircraft.

With reference to FIG. 2, a schematic side view of the braiding machine16 is illustrated. The braiding machine 16 includes a braiding mechanism28 and a mandrel 30. The braiding mechanism 28 is configured to braid aunidirectional tape 32 or unidirectional tow onto the mandrel 30, aswill be described below. The mandrel 30 is supported and advanced by aholder 31 along a center axis “A” of the braiding mechanism 28.

With reference to FIG. 3 and continued reference to FIG. 2, anillustration of the braiding machine 16 viewed in the direction ofsection line 3-3 in FIG. 2 is shown. The braiding mechanism 28 includesa carrier 34 supported by a base plate 36. The carrier 34 is ring-shapedand defines an aperture 34A. The mandrel 30 passes through the aperture34A during braiding along center axis “A”. A number of spools 38 aremounted to the carrier 34. The spools 38 are each moveable relative tothe mandrel 30 annularly about the center axis of the carrier 34. Theunidirectional tape 32 is wound around each of the spools 38. While inFIG. 2 five spools 38 are schematically shown and in FIG. 3 numerousspools 38 are illustrated, it should be appreciated that any number ofspools 38 may be used depending on the desired properties of the tubularbraiding 22. For example, in one non-limiting embodiment the braidingmechanism 28 includes as few as forty spools 38 or as many as twohundred spools 38. The spools 38 generally include warp spools 38A andweft spools 38B. The warp spools 38A are moved in a clockwise directionC (shown in FIG. 3) by the carrier 34 and the weft spools 38B in acounter-clockwise direction CC (shown in FIG. 3) by the carrier 34. Thewarp spools 38A and the weft spools 38B are preferably moved at the samespeed.

The braiding mechanism 28 further includes a guide ring 40 positionedaround the mandrel 30. The guide ring 40 directs the unidirectional tape32 wound around a corresponding spool 38 onto the mandrel 30.Specifically, the unidirectional tape 32 is directed from acorresponding spool 38 onto the mandrel 30 through a convergence zone42. The point where the unidirectional tape 32 first comes into contactwith the mandrel 30 is denoted as a fell point 44.

The mandrel 30 acts as a substrate on which the unidirectional tape 32is braided by the braiding mechanism 28 to form the tubular braiding 22.The mandrel 30 may have various shapes but is preferably an elongatedcylinder. In one embodiment, the diameter of the mandrel 30 is 2 inches.However, it should be appreciated that the mandrel 30 may have otherdiameters depending on the design requirements of the compositestructure 26. In one embodiment, the size or volume of the mandrel 30may be controlled. For example, the mandrel 30 is an inflatable tube,such as a silicon bladder. However, in another embodiment, the mandrel30 has a fixed size or volume. For example, the mandrel 30 isconstructed of a solid semi-rigid material such as, but not limited to,ethylene propylene diene monomer (EPDM), rubber, silicone, neoprene, ornatural rubber. In yet another embodiment, the mandrel 30 is constructedof a thin film polymer compatible with the composition of theunidirectional tape 32.

An inflation mechanism 48 is connected to the mandrel 30 by a supplyline 50. The inflation mechanism 48 provides pressurized air or anothergas or liquid to the mandrel 30. The inflation mechanism 48 cycles themandrel 30 between a deflated state and an inflated state.

Turning briefly to FIG. 4, an enlarged view of the unidirectional tape32, indicated by Section view 4-4 in FIG. 2, is shown. Theunidirectional tape 32 comprises unidirectional fibers 54 in acontinuous strip held together by thermal or adhesive bonding. Theunidirectional fibers 54 are parallel with one another. In oneembodiment, the unidirectional fibers 54 are pre-impregnated with aresin. In one embodiment, the resin is a thermoplastic such as, forexample polyphenylene sulfide (PPS), polyether ether ketone (PEEK),polyether ketone ketone (PEKK), etc. However, in another embodiment, theresin is a thermoset resin such as, for example, epoxy, cyanate ester,etc. In still another embodiment, the unidirectional fibers 54 are heldtogether by relatively fine holding threads (not shown). The holdingthreads are not woven with the unidirectional fibers 54. Instead, theholding threads are deposited on the top and bottom sides of theunidirectional tape 32. In another embodiment, the unidirectional tape32 is comprised of a unidirectional tow. A unidirectional tow includesunidirectional fibers that are held together by stitching threadscrossing over several carbon tows. In still other embodiments, theunidirectional tape 32 is constructed of a slit-tape thermoplastic, athermoset tape that is substantially tack-free at room temperature, abindered dray roving prepreg wherein an epoxy or thermoplastic binder isapplied, a substantially tack-free thermoset prepreg, or a low tackthermoset prepreg.

Returning to FIGS. 2 and 3, the operation of the braiding machine 16 iscontrolled by a control module 52 (shown in FIG. 2). The control module52 is in communication with the braiding mechanism 28, the holder 31,and the inflation mechanism 48. The control module 52 may refer to, orbe part of an electronic circuit, a combinational logic circuit, a fieldprogrammable gate array (FPGA), a processor (shared, dedicated, orgroup) that executes code, or a combination of some or all of the above,such as in a system-on-chip. Additionally, the control module 52 may bemicroprocessor-based such as a computer having a at least one processor,memory (RAM and/or ROM), and associated input and output buses. Theprocessor may operate under the control of an operating system thatresides in memory. The operating system may manage computer resources sothat computer program code embodied as one or more computer softwareapplications, such as an application residing in memory, may haveinstructions executed by the processor. In an alternative embodiment,the processor may execute the application directly, in which case theoperating system may be omitted.

The control module 52 controls movement of the mandrel 30 via the holder31 and movement of the spools 38 to braid the unidirectional tape 32onto the mandrel 30 to form the tubular braiding 22. For example, thecontrol module 52 executes instructions to inflate the mandrel 30 to theinflated state by commanding the inflation mechanism 48 to providepressurized air to the mandrel 30. The control module 52 executesinstructions to guide movement of the mandrel 30 in an axial direction‘A’ (shown in FIG. 2) through the carrier 34. As the mandrel 30 movesthrough the carrier 34, the control module 52 executes instructions tomove the warp spools 38A in the clockwise C direction and the weftspools 38B in the counter clockwise CC direction around the mandrel 30.The unidirectional tape 32 is pulled from a corresponding spool 38. Theunidirectional tape 32 from the warp spools 38A and the weft spools 38Binterlock or weave together with one another to create the tubularbraiding 22 on the mandrel 30. In one embodiment, the control module 52receives an indication that the unidirectional tape 32 is wound aroundthe mandrel 30. Specifically, the indication means that the braidingmachine 16 has finished placing the unidirectional tape 32 onto themandrel 30 to create the tubular braiding 22. For example, theindication may be a manual input from a user. Alternatively, a sensormay provide an indication that the braiding machine 16 has finishedcreating the tubular braiding 22. In response to receiving theindication, the control module 52 instructs the inflation mechanism 48to release air to deflate the mandrel 30.

In the embodiment where the mandrel 30 is not inflatable, the tubularbraiding 22 is slit to remove the mandrel 30. For example, a cuttingmachine (not shown) or worker may be used to slit the tubular braiding22 along an entire length thereof, thus allowing the mandrel 30 to beremoved. An example of a slit 55 is shown by dashed line in FIG. 2.Alternatively, where the mandrel 30 is comprised of the thin filmpolymer compatible with the composition of the unidirectional tape 32,the mandrel 30 remains with, and forms part of, the tubular braiding 22.

In an alternative embodiment, the control module 52 executesinstructions to provide air via the inflation mechanism 48 to inflatethe mandrel 30 only partially. Once the control module 52 receives anindication that the unidirectional tape 32 is wound around the mandrel30, the control module 52 then executes instructions to provide air bythe inflation mechanism 48 to further inflate the mandrel 30, which inturn places the unidirectional fibers 54 into tension. Alternatively,the mandrel 30 may remain partially inflated during the braiding. Fullyinflating the mandrel 30 allows for near-zero fiber angle lay-up andavoids any collapse or volume shrinkage of the mandrel 30 where thebraid of unidirectional tape 32 is tight. Partially inflating themandrel 30 to a point where the mandrel is geometrically stable allowsfor a relatively flexible or loose braid of unidirectional tape 32.This, in turn, allows the unidirectional tape 32 to slip or shear duringwinding and forming, as described below. In both cases, controlling thesize or volume of the mandrel 30 provides the ability to customize ageometry of the tubular braiding 22 that is braided onto the mandrel 30.

FIG. 5 shows an enlarged portion of the tubular braiding 22 viewed inthe direction of arrows 5-5 in FIG. 2. In the example provided, thetubular braiding 22 includes a biaxial braid 56. In the biaxial braid56, a matrix of parallel unidirectional tape 32A are interwoven orbraided into an matrix of orthogonal parallel unidirectional tape 32B.The parallel unidirectional tape 32A is disposed at a bias angle α tothe orthogonal parallel unidirectional tape 32B. The bias angle α isdetermined based on the specific application, however steeper braidangles result in increased flexibility. However, angle α may change whenthe unidirectional tape is wound or formed, as described below.

Returning back to FIG. 2, the braiding machine 16 may also be configuredto form a tubular braiding 22 having a triaxial braid. To form a tubularbraiding 22 with a triaxial braid, the unidirectional tape 32 isinserted along a length “L” of the mandrel 30 from fixed spools 32C(only one of which is shown). The fixed spools 32C do not rotate alongthe frame 34. It should be appreciated that any number of fixed spools32C may be employed.

FIG. 6 shows an enlarged portion of the tubular braiding 22 with atriaxial braid 58 viewed in the direction of arrows 6-6 in FIG. 2. Thetriaxial braid 58 is similar to the biaxial braid 56 (FIG. 5), however,an additional matrix of parallel unidirectional tape 32C, extending theaxial length of the tubular braiding 22 parallel to the center axis “A”(FIG. 2), is interwoven into the parallel unidirectional tape 32A andorthogonal parallel unidirectional tape 32B. The unidirectional tape 32Cis supplied from the fixed spools 32C. Again, the bias angle α maychange when the unidirectional tape is wound or formed, as describedbelow. The triaxial braid 58 may provide enhanced structural strength inthe longitudinal direction of the tubular braiding 22.

With reference to FIG. 7, and continued reference to FIGS. 2-6, a flowdiagram is shown illustrating a method 100 of forming the tubularbraiding 22 where a size or volume of the mandrel 30 is controlled. Themethod 100 begins at block 102. In block 102, the control module 52controls the size or volume of the mandrel 30 prior to braiding. In oneexample, the mandrel 30 is inflatable by the inflation mechanism 48.Thus, the control module 52 instructs the inflation mechanism 48 toprovide air to inflate the mandrel 30. In one embodiment, the mandrel 30is inflated fully. In another embodiment, the mandrel 30 is partiallyinflated. The method 100 then proceeds to block 104.

In block 104, the method 100 includes braiding the unidirectional tape32 around the mandrel 30 to form the tubular braiding 22. For example,the control module 52 commands the mandrel 30 to move axially in thedirection “A” while commanding the spools 38 to rotate, thus forming abraid of unidirectional tape 32 on the mandrel 30, as described above.Depending on the configuration of the braiding mechanism 28, one of abiaxial braid 56 (FIG. 5) or a triaxial braid 58 (FIG. 6) is formed onthe mandrel 30 and the method 100 proceeds to block 106 or block 108.

In block 106, the braiding machine 16 braids the tubular braiding 22with the biaxial braid 56 (FIG. 5). In block 108, the braiding machine16 braids the tubular braiding 22 with the triaxial braid 58 (FIG. 6).In either case, the method 100 proceeds to block 110.

In block 110, the control module 52 controls the size or volume of themandrel 30 after the braiding is complete. For example, the controlmodule 52 instructs the inflation mechanism 48 to deflate the mandrel30, thus allowing the tubular braiding 22 to be easily removed from themandrel 30.

With reference to FIG. 8, and continued reference to FIGS. 2-6, a flowdiagram is shown illustrating a method 200 of forming the tubularbraiding 22 where the mandrel 30 is not inflatable. The method 200begins at block 202. In block 202, the method 200 includes placing theunidirectional tape 32 on the mandrel 30. For example, a combination ofunidirectional tape 32A, 32B, or 32C may be placed on the mandrel 30.The method 200 then proceeds to block 204.

At block 204 the control module 52 commands the mandrel 30 to moveaxially along the center axis “A” (FIG. 2). At block 206, the controlmodule 52 commands the warp spools 38A and the weft spools 38B tocounter rotate about the center axis “A” as the mandrel 30 moves alongthe center axis “A”. Depending on which type of braid 56, 58 (FIGS. 5,6) is to be produced, the method 200 proceeds to either block 208 orblock 210.

At block 208 the unidirectional tape 32A, 32B are interlaced together toform the biaxial braid 56 (FIG. 5). For example, as the mandrel 30 movesalong the center axis “A”, the warp spools 38A and the weft spools 38Bcounter-rotate. Movement of the mandrel 30 draws out the unidirectionaltape 32 disposed on the warp spools 38A and the weft spools 38B. Thecounter-rotation of the warp spools 38A and the weft spools 38Binterlaces the unidirectional tape 32A from the warp spools 38A with theunidirectional tape 32B from the weft spools 38B as the mandrel 30 movesalong the center axis “A” (FIG. 2). At block 212 the tubular braiding 22has been formed with a biaxial braid 56 (FIG. 5).

At block 210 the unidirectional tape 32A, 32B, and 32C are interlacedtogether to form the triaxial braid 58 (FIG. 6). For example, as themandrel 30 moves along the center axis “A”, the warp spools 38A and theweft spools 38B counter-rotate. Movement of the mandrel 30 draws out theunidirectional tape 32A disposed on the warp spools 38A, theunidirectional tape 32B disposed on the weft spools 32B, and theunidirectional tape 32C disposed on the fixed spools 38C. Thecounter-rotation of the warp spools 38A and the weft spools 38Binterlaces the unidirectional tape 32A from the warp spools 38A with theunidirectional tape 32B from the weft spools 38B and with theunidirectional tape 32C from the fixed spools 38C as the mandrel 30moves along the center axis “A” (FIG. 2). At block 214 the tubularbraiding 22 has been formed with a triaxial braid 58 (FIG. 6).

In either case, the method 200 ends when the tubular braiding 22 hasbeen formed. Where the mandrel 30 is removable, the method 200 may alsoinclude slitting the tubular braiding 22 along an entire length thereofto assist in removing the mandrel 30. Where the mandrel 30 is formed ofthe thin film polymer compatible with the composition of theunidirectional tape 32, the mandrel 30 remains with, and forms part of,the tubular braiding 22.

Turning to FIG. 9, the winding tool 18 will now be described. Thewinding tool 18 generally includes a body portion 60 that extendsvertically It should be appreciated that in other embodiments the bodyportion 60 may extend horizontally or at an angle. The body portion 60has an outer surface 62. The outer surface 62 generally conforms to ashape of the composite structure 26. Thus, a cross-sectional shape ofthe body portion 60 varies depending on the final shape of the compositestructure 26. In the example provided, the body portion 60 has arectangular cross-section with rounded corners 64. However, as shown inFIG. 9A, the body portion 60 may have a circular cross-section.Alternatively, as shown in FIG. 9B, the body portion 60 may have anelliptical or oval cross-section. It should be appreciated that the bodyportion 60 may have additional cross-sections without departing from thescope of the present disclosure.

With reference to FIG. 10, to form the wound tubular braiding 24, thetubular braiding 22 is wound around the outer surface 62 of the windingtool 18. The tubular braiding 22 may be wound around the winding tool 18manually or in an automated process using a device 65, such as a roboticarm or manipulator, etc. The wound tubular braiding 24 is comprised ofstacked turns 66 of the tubular braiding 22. While in the exampleprovided five stacked turns 66 are shown, it should be appreciated thatthe tubular braiding 22 may be wound around the winding tool 18 anynumber of times producing any number of stacked turns 66. It should beappreciated that the number of stacked turns 66 is dependent upon thenumber of plies desired in the composite structure 26 and the thicknessof the composite structure 26. Where the tubular braiding 22 has thetriaxial braid 58, the unidirectional tape 32C (FIG. 6) is orientatedroughly parallel to the outer surface 62 of the winding tool 18 when thetubular braiding 22 is wound around the winding tool 18. Thus, theunidirectional tape 32C (FIG. 6) is disposed roughly parallel to anaperture and or an outer perimeter of the composite structure 26.

Once the wound tubular braiding 24 is formed, the wound tubular braiding24 is separated from the winding tool 18, as shown in FIG. 11. The woundtubular braiding 24 may be separated from the winding tool 18 manuallyor in an automated process using a robotic arm or manipulator (notshown), etc. The wound tubular braiding 24 has a first free end 24A anda second free end 24B. As seen in FIG. 11, the wound tubular braiding 24has a helical or spiral shape and is formed of a single length oftubular braiding 22. The wound tubular braiding 24 is hollow and definesa central bore 24C that extends throughout the wound tubular braiding24. When separated from the winding tool 18, the wound tubular braiding24 has sufficient strength to maintain the overall shape that wasprovided by the winding tool 18. To form the composite structure 26, thewound tubular braiding 24 is placed in the forming machine 20, as willbe described below.

FIG. 12 shows a front perspective view of the forming machine 20 in anopen position. The forming machine 20 includes an upper die plate 70 anda lower die plate 72. In the example provided, the upper die plate 70may be lowered on support members 74 via an electric motor 75 to matewith the lower die plate 72 in a closed position. Alternatively, theupper die plate 70 and the lower die plate 72 may be hinged together(not shown). The lower die plate 72 includes a lower mold surface 76 anda forming mandrel 78 extending from the lower mold surface 76. Theforming mandrel 78 is substantially the same size the cross section ofthe winding tool 18. A heating element 80 is disposed within the lowerdie plate 72. The heating element 80 is configured to heat the lowermold surface 76. In the example provided, the heating element 80includes electrical wires that heat the lower mold surface 76 viaresistance heating. Alternatively, the heating element 80 may includehot oil pumped through tubes (not shown), inductive heaters, externalheaters, etc. The upper die plate 70 and/or the forming mandrel 78 mayalso include a heating element (not shown) without departing from thescope of the present disclosure.

FIG. 13 shows a cross-section of the forming machine 20 in the closedposition with the upper die plate 70 mated with the lower die plate 72.The upper die plate 70 includes an upper mold surface 82. An outer moldsurface 83 extends down from the upper mold surface 82. A recess 84 isformed in the upper mold surface 82. When in the closed position, theforming mandrel 78 of the lower die plate 72 is mated within the recess84 of the upper die plate 70. Additionally, the lower mold surface 76,the forming mandrel 78, the upper mold surface 82, and the outer moldsurface 83 cooperate to define a mold cavity 86 between the upper dieplate 70 and the lower die plate 72. The mold cavity 86 surrounds theforming mandrel 78.

In one embodiment, the forming machine 20 further includes a vacuumsource 88 that communicates with a vacuum port 90. The vacuum port 90 isdisposed in the lower mold surface 76 and communicates with the moldcavity 86. The vacuum source 88 generates a vacuum in the mold cavity 86to removes excess air, gases and voids from wound tubular braiding 24during forming. The vacuum port 90 may alternatively, or in addition, bedisposed in the upper mold surface 82.

The forming machine 20 further includes a controller 92 in communicationwith the electric motor 75, the heating element 80, and the vacuumsource 88. The controller 92 may also be in communication with thedevice 65 used to wind the tubular braiding 22 around the winding tool18 (see FIG. 10). The controller 92 may refer to, or be part of anelectronic circuit, a combinational logic circuit, a field programmablegate array (FPGA), a processor (shared, dedicated, or group) thatexecutes code, or a combination of some or all of the above, such as ina system-on-chip. Additionally, the controller 92 may bemicroprocessor-based such as a computer having a at least one processor,memory (RAM and/or ROM), and associated input and output buses. Theprocessor may operate under the control of an operating system thatresides in memory. The operating system may manage computer resources sothat computer program code embodied as one or more computer softwareapplications, such as an application residing in memory, may haveinstructions executed by the processor. In an alternative embodiment,the processor may execute the application directly, in which case theoperating system may be omitted.

The controller 92 controls movement of the upper die plate 70 and thelower die plate 72 via the electric motor 75. The controller 92 alsocontrols the temperature that is applied to the mold cavity 86 duringforming of the wound tubular braiding 24 into the composite structure 26via the heating element 80. In one example, the controller 92 controlsthe temperature in the mold cavity 86 based on the type of resin used inthe unidirectional tape 32 (FIG. 4) that makes up the wound tubularbraiding 24. In one embodiment the thermoplastic resin includes a resinmelt temperature that ranges from about 205° C. to over 400° C., and athermoset resin includes a resin melt temperature of about 177° C. Asused herein, the term “about” is known to those skilled in the art.Alternatively, the term “about” means +/−10° C. The controller 92 alsocontrols the rate at which the mold cavity 86 is cooled to ensurecross-linking of the thermoset polymer in the unidirectional tape 32.The controller 92 also controls applying a vacuum to the mold cavity 86via the vacuum source 88. As noted above, the vacuum removes excess air,gas, volatiles, and voids from the wound tubular braiding 24 in the moldcavity 86. In one embodiment, the controller 92 also controls resininfusion (not shown) of the wound tubular braiding 24 during forming.Resin infusion may be desirable where the unidirectional tape 32 employsa thermoset resin and where the unidirectional fibers 54 are tackedtogether with a binder into tows or tapes. The tacking provides enoughbinder to hold non-impregnated fibers together in tows of tape. Theresin infusion impregnates the unidirectional fibers 54 with the resin

With reference to FIGS. 14 and 15, the forming machine 20 is shown withthe wound tubular braiding 24 disposed therein prior to forming. Thewound tubular braiding 24 is disposed on the lower mold surface 76 andaround the forming mandrel 78. Thus, the wound tubular braiding 24maintains the helical or spiral winding when disposed within the formingmachine 20.

FIG. 16 shows the forming machine 20 in the closed position with thewound tubular braiding 24 disposed therein. To form the compositestructure 26, the wound tubular braiding 24 is consolidated, i.e.compressed, by the upper die plate 70 and lower die plate 72 within themold cavity 86. For example, the controller 92 executes instructions toactuate the upper die plate 70 and the lower die plate 72 towards oneanother via the electric motor 75 until the upper die plate 70 ispressed against the lower die plate 72. Pressing the upper die plate 70against the lower die plate 72 consolidates the wound tubular braiding24. Next, the controller 92 applies heat to the wound tubular braiding24 via the heating element 80. As noted above, the temperature that isset, as well as the heating time and cooling time, is determined basedon factors related to the material of the resin used in the woundtubular braiding 24. In one example, the temperature is from about 205°C. to over 400° C. and in another example the temperature is set toabout 177° C. Either before or during heating, the controller 92 appliesa vacuum to the mold cavity 86 via the vacuum source 88 to remove excessair, gas, volatiles, and voids from the wound tubular braiding 24 duringconsolidation and/or heating. Once consolidation, heating, and cool offhas been accomplished, the controller 92 commands the electric motor 75to open the forming machine 20 and the composite structure 26 isremoved. The composite structure 26 may be removed manually or via arobotic arm or manipulator (not shown).

In one embodiment, the composite structure 26 is over-molded to createadditional features such as, for example, connectors or ribs (notshown). The composite structure 26 may also be trimmed in order toachieve a final profile.

FIG. 17 shows an example of the composite structure 26 formed using thebraiding machine 16, winding tool 18, and forming machine 20 describedabove. The composite structure 26 includes a frame portion 94 thatdefines an aperture 96. In the example provided the composite structure26 is illustrated as a window frame for an aircraft. However, it is tobe appreciated that the composite structure 26 may be any component thatdefines an aperture, and especially any component that also includestight corners or radiuses. For example, in another embodiment thecomposite structure 26 may be a door frame or any other type of accessframe. Referring back to FIG. 16, the lower mold surface 76, the uppermold surface 82, and the forming mandrel 78 cooperate to define theshape of the frame portion 94. In particular, the shape of the aperture96 corresponds to the shape of the forming mandrel 78, which in turncorresponds to the shape of the winding tool 18 (FIG. 9). Thus, the bodyportion 60 of the winding tool 18 has roughly the shape of the aperture96 and the outer edges of the wound tubular braiding 24 (FIG. 11) formthe outer perimeter of the composite structure 26. Where the tubularbraiding 22 has the triaxial braid 58, the unidirectional tape 32C (FIG.6) is disposed roughly parallel to a perimeter of the aperture 96.Returning to FIG. 17, during forming in the forming machine 20, thetubular braiding 22 (FIGS. 5 and 6) of the wound tubular braiding 24 iscompacted flat when consolidated. In other words, the compositestructure 26 has a solid cross-section.

FIG. 18 shows an enlarged, cross-section of the composite structure 26viewed in the direction of section line 18-18 in FIG. 17. The compositestructure 26 has a composite laminate structure 98 that includes aplurality of plies 99. Each of the plurality of plies 99 corresponds toa stacked turn 66 (FIG. 10) of the wound tubular braiding 24. Thus, eachof the plurality of plies 99 include either a flattened biaxial braid 56(FIG. 5) or a flattened triaxial braid 58 (FIG. 6). During consolidationand heating, the resin of the unidirectional tape 32 (FIGS. 5 and 6)forms a polymer matrix such that the plurality of plies 99 are definedby orientation of the unidirectional fibers 54 (FIG. 4) that forms theunidirectional tape 32. For each of the plurality of plies 99, eitherthe biaxial braid 56 or the triaxial braid 58 are oriented to form ahoop type configuration with a large volume of the unidirectional fibers54 in the desire direction, thus increasing the efficiency of thecomposite structure 26. In other words, the unidirectional fibers 54(FIG. 4) are oriented in the same direction for each of the plurality ofplies 99 at any given cross section. The composite laminate structure 98includes a predefined fiber to volume ratio, which may also be referredto as a fiber volume ratio. The fiber volume ratio represents thepercentage of unidirectional fibers 54 in the composite laminatestructure 98. Mechanical properties of a composite structure such as,but not limited to, tensile strength depend upon the fiber to volumeratio. Thus, the fiber to volume ratio of the composite laminatestructure 98 is determined based on a specific application orrequirements.

It is to be appreciated that the forming machine 20 consolidates thewound tubular braiding 24 into a near net shape. As a result, thecomposite structure 26 requires less trimming to create a final profilewhen compared to conventional processes. Furthermore, the extensivepost-processing and machining that is typically required to fabricate acomposite structure is no longer needed.

Turning now to FIG. 19, an exemplary process flow diagram illustrates amethod 300 for fabricating the composite structure 26 using the system10 described above in FIGS. 1-18. The method 300 beings at block 302. Inblock 302, the method 300 includes placing the unidirectional tape 32 onthe mandrel 30. For example, a combination of unidirectional tape 32A,32B, or 32C may be placed on the mandrel 30. The method 300 thenproceeds to block 304.

At block 304 the control module 52 commands the mandrel 30 to moveaxially along the center axis “A” (FIG. 2). At block 306, the controlmodule 52 commands the warp spools 38A and the weft spools 38B tocounter rotate about the center axis “A” as the mandrel 30 moves alongthe center axis “A”. Depending on which type of braid 56, 58 (FIGS. 5,6) is to be produced, the method 300 proceeds to either block 308 orblock 310.

At block 308 the unidirectional tape 32A, 32B are interlaced together toform the biaxial braid 56 (FIG. 5). For example, as the mandrel 30 movesalong the center axis “A”, the warp spools 38A and the weft spools 38Bcounter-rotate. Movement of the mandrel 30 draws out the unidirectionaltape 32 disposed on the warp spools 38A and the weft spools 38B. Thecounter-rotation of the warp spools 38A and the weft spools 38Binterlaces the unidirectional tape 32A from the warp spools 38A with theunidirectional tape 32B from the weft spools 38B as the mandrel 30 movesalong the center axis “A” (FIG. 2). At block 312 the tubular braiding 22has been formed with a biaxial braid 56 (FIG. 5).

At block 310 the unidirectional tape 32A, 32B, and 32C are interlacedtogether to form the triaxial braid 58 (FIG. 6). For example, as themandrel 30 moves along the center axis “A”, the warp spools 38A and theweft spools 38B counter-rotate. Movement of the mandrel 30 draws out theunidirectional tape 32A disposed on the warp spools 38A, theunidirectional tape 32B disposed on the weft spools 32B, and theunidirectional tape 32C disposed on the fixed spools 38C. Thecounter-rotation of the warp spools 38A and the weft spools 38Binterlaces the unidirectional tape 32A from the warp spools 38A with theunidirectional tape 32B from the weft spools 38B and with theunidirectional tape 32C from the fixed spools 38C as the mandrel 30moves along the center axis “A” (FIG. 2). At block 314 the tubularbraiding 22 has been formed with a triaxial braid 58 (FIG. 6). Dependingon the configuration of the mandrel 30 as noted above, the mandrel 30may be separated from the tubular braiding 22 or left in the tubularbraiding 22. From block 312 or block 314, the method 300 proceeds toblock 316.

Block 316 includes winding the tubular braiding 22 around the windingtool 18. The winding of the tubular braiding 22 forms the wound tubularbraiding 24 (FIG. 11). As noted above, the winding may be done manuallyor via an automated process using the device 65. The method 300 thenproceeds to block 318.

Block 318 includes forming the wound tubular braiding 24 into thecomposite structure 26. For example, the wound tubular braiding 24 maybe placed into the forming machine 20 (FIGS. 14-15). The controller 92then consolidates, i.e. flattens, the wound tubular braiding 24 to formthe plies 99 (FIG. 18). The controller 92 then heats the wound tubularbraiding 24 to form the composite structure 26 (FIG. 16).

Referring to FIG. 20, an exemplary process flow diagram illustrates amethod 400 for forming the winding of tubular braiding 22 using thesystem 10 described above in FIGS. 1-11. The method 400 beings at block402. In block 402, the method 400 includes placing the unidirectionaltape 32 on the mandrel 30. For example, a combination of unidirectionaltape 32A, 32B, or 32C may be placed on the mandrel 30. The method 400then proceeds to block 404.

At block 404 the control module 52 commands the mandrel 30 to moveaxially along the center axis “A” (FIG. 2). At block 406, the controlmodule 52 commands the warp spools 38A and the weft spools 38B tocounter rotate about the center axis “A” as the mandrel 30 moves alongthe center axis “A”. Depending on which type of braid 56, 58 (FIGS. 5,6) is to be produced, the method 400 proceeds to either block 408 orblock 410.

At block 408 the unidirectional tape 32A, 32B are interlaced together toform the biaxial braid 56 (FIG. 5). For example, as the mandrel 30 movesalong the center axis “A”, the warp spools 38A and the weft spools 38Bcounter-rotate. Movement of the mandrel 30 draws out the unidirectionaltape 32 disposed on the warp spools 38A and the weft spools 38B. Thecounter-rotation of the warp spools 38A and the weft spools 38Binterlaces the unidirectional tape 32A from the warp spools 38A with theunidirectional tape 32B from the weft spools 38B as the mandrel 30 movesalong the center axis “A” (FIG. 2). At block 412 the tubular braiding 22has been formed with a biaxial braid 56 (FIG. 5).

At block 410 the unidirectional tape 32A, 32B, and 32C are interlacedtogether to form the triaxial braid 58 (FIG. 6). For example, as themandrel 30 moves along the center axis “A”, the warp spools 38A and theweft spools 38B counter-rotate. Movement of the mandrel 30 draws out theunidirectional tape 32A disposed on the warp spools 38A, theunidirectional tape 32B disposed on the weft spools 32B, and theunidirectional tape 32C disposed on the fixed spools 38C. Thecounter-rotation of the warp spools 38A and the weft spools 38Binterlaces the unidirectional tape 32A from the warp spools 38A with theunidirectional tape 32B from the weft spools 38B and with theunidirectional tape 32C from the fixed spools 38C as the mandrel 30moves along the center axis “A” (FIG. 2). At block 414 the tubularbraiding 22 has been formed with a triaxial braid 58 (FIG. 6). Dependingon the configuration of the mandrel 30 as noted above, the mandrel 30may be separated from the tubular braiding 22 or left in the tubularbraiding 22. From block 412 or block 414, the method 400 proceeds toblock 416. Block 416 includes winding the tubular braiding 22 around thewinding tool 18. The winding of the tubular braiding 22 forms the woundtubular braiding 24 (FIG. 11). As noted above, the winding may be donemanually or via an automated process using the device 65. The method 400then proceeds to block 418.

Block 418 includes slipping or shearing the unidirectional tape 32(FIGS. 5-6) relative to one another while winding the tubular braiding22 around the winding tool 18. It is to be appreciated that theunidirectional tape 32 slips or shears relative to one another withoutbending when the tubular braiding 22 is wound around the winding tool18. This results in a wound tubular braiding 24 having an increasednumber of unidirectional tape 32 oriented in the same direction as theperimeter of the composite structure 26, which in turn provides improvedload bearing capabilities. The disclosed process for fabricating thecomposite structure 26 is faster when compared to conventional lay-upprocesses, thereby enabling higher production rates. Finally, thedisclosed process creates less wasted material when compared toconventional processes.

Embodiments of the system 10 described above, as well as the methods100, 200, 300, and 400, may be employed in the context of an aircraftmanufacturing and service method 500 as shown in FIG. 21 and an aircraft502 as shown in FIG. 22. During pre-production, exemplary method 500 mayinclude specification and design 504 of the aircraft 502 and materialprocurement 506. During production, component and subassemblymanufacturing 508 and system integration 510 of the aircraft 502 takesplace. Thereafter, the aircraft 502 may go through certification anddelivery 512 in order to be placed in service 514. While in service by acustomer, the aircraft 502 is scheduled for routine maintenance andservice 516 (which may also include modification, reconfiguration,refurbishment, and so on).

Each of the processes of the systems and methods described herein may beperformed or carried out by a system integrator, a third party, and/oran operator (e.g., a customer). For the purposes of this description, asystem integrator may include without limitation any number of aircraftmanufacturers and major-system subcontractors; a third party may includewithout limitation any number of venders, subcontractors, and suppliers;and an operator may be an airline, leasing company, military entity,service organization, and so on.

As shown in FIG. 22, the aircraft 502 produced by exemplary method 500may include an airframe 518 with a plurality of systems 520 and aninterior 522. Examples of high-level systems 520 include one or more ofa propulsion system 524, an electrical system 526, a hydraulic system526, and an environmental system 530. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of theinvention may be applied to other industries, such as the automotiveindustry.

The system and methods described above may be employed during any one ormore of the stages of the production and service method 500. Forexample, components or subassemblies corresponding to production process508 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 502 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 508 and 510, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 502. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft502 is in service, for example and without limitation, to maintenanceand service 516. Embodiments of the system 10 described above, as wellas the methods 100, 200, 300, and 400, may be employed with thecomponent and subassembly manufacturing 508, the system integration 510,the routine maintenance and service 516, the airframe 518, and theinterior 522.

The description of the present disclosure is merely exemplary in natureand variations that do not depart from the gist of the presentdisclosure are intended to be within the scope of the presentdisclosure. Such variations are not to be regarded as a departure fromthe spirit and scope of the present disclosure.

What is claimed is:
 1. A composite structure, comprising: a tubularbraiding that has a biaxial braid.
 2. The composite structure of claim1, wherein biaxial braid includes a matrix of parallel unidirectionaltape braided into a matrix of orthogonal parallel unidirectional tape.3. The composite structure of claim 1, wherein the tubular braiding isconstructed of a material selected from the group consisting of: aunidirectional tape and a unidirectional tow.
 4. The composite structureof claim 3, wherein the unidirectional tape is constructed ofunidirectional fibers.
 5. The composite structure of claim 4, whereinthe unidirectional fibers are pre-impregnated with a resin.
 6. Thecomposite structure of claim 5, wherein the resin a thermoset.
 7. Thecomposite structure of claim 5, wherein the resin is a thermoplastic. 8.The composite structure of claim 1, wherein the tubular braiding isconstructed of a material selected from the group consisting of: aslit-tape thermoplastic, a thermoset tape that is substantiallytack-free at room temperature, a bindered dray roving prepreg wherein anepoxy or thermoplastic binder is applied, a substantially tack-freethermoset prepreg, and a low tack thermoset prepreg.
 9. The compositestructure of claim 1, wherein the composite structure is comprised of aformed winding of the tubular braiding.
 10. An apparatus for fabricatinga composite structure of wound tubular braiding, the apparatuscomprising: a winding tool defining an outer surface; a device to windthe tubular braiding around the outer surface of the winding tool tocreate a wound tubular braiding; a forming machine to consolidate thewound tubular braiding; and a controller in electronic communicationwith the device and the forming machine, wherein the controller executesinstructions to: guide the device to wind the tubular braiding aroundthe outer surface of the winding tool; and operate the forming machineto consolidate the wound tubular braiding.
 11. The apparatus of claim10, wherein the device is a robotic arm.
 12. The apparatus of claim 10,wherein the controller executes instructions to: wind the tubularbraiding, by the device, around the winding tool into a spiral pattern.13. The apparatus of claim 10, wherein the composite structure definesan aperture.
 14. The apparatus of claim 13, wherein the outer surface ofthe winding tool corresponds to the aperture of the composite structure.15. The apparatus of claim 10, wherein the forming machine includes anupper die plate and a lower die plate.
 16. The apparatus of claim 15,wherein the upper die plate includes an upper mold surface and the lowerdie plate includes a lower mold surface.
 17. The apparatus of claim 16,further comprising a forming mandrel extending from the lower moldsurface.
 18. The apparatus of claim 15, wherein the controller executesinstructions to: actuate the upper die plate and the lower die platetowards one another until the upper die plate is pressed against thelower die plate.
 19. The apparatus of claim 18, wherein pressing theupper die plate against the lower die plate consolidates the woundtubular braiding.
 20. The apparatus of claim 18, wherein the lower dieplate includes a heating element in electronic communication with thecontroller.
 21. The apparatus of claim 20, wherein the controllerexecutes instructions to: determine the upper die plate and the lowerdie plate are pressed against one another; and in response todetermining the upper die plate and the lower die plate are pressedagainst one another, activate the heating element to produce heat. 22.The apparatus of claim 21, wherein the controller executes instructionsto activate the heating element to a resin melt temperature.
 23. Theapparatus of claim 22, wherein the resin melt temperature is one of athermoplastic melt temperature and a thermoset melt temperature.
 24. Amethod of forming a tubular braiding, the method comprising: braiding aunidirectional tape into the tubular braiding.
 25. The method of claim24, further comprising braiding the unidirectional tape around a mandrelto form the tubular braiding.
 26. The method of claim 25, wherein themandrel is inflatable.
 27. The method of claim 26, further comprisingproviding air by an inflation mechanism to inflate the mandrel.
 28. Themethod of claim 27, further comprising inflating the mandrel into apredetermined shape.
 29. The method of claim 28, further comprisingwinding the unidirectional tape around the mandrel after inflated intothe predetermined shape.
 30. The method of claim 29, further comprisingdeflating the mandrel by releasing air by the inflation mechanism. 31.The method of claim 25, wherein the mandrel is constructed of asemi-rigid material.
 32. The method of claim 24, further comprisingpre-impregnating the unidirectional tape with a resin.
 33. The method ofclaim 24, wherein the unidirectional tape comprises unidirectionalfibers.
 34. The method of claim 24, further comprising braiding theunidirectional tape into a tubular braiding having a biaxial braid. 35.The method of claim 24, further comprising braiding the unidirectionaltape into a tubular braiding having a triaxial braid.